There is provided an exposure control apparatus including a photometry amount acquisition unit for acquiring a measured light amount as a photometry amount; a light emission amount control unit for increasing a light emission amount of a light emission unit as the photometry amount is smaller when the photometry amount is within a certain light amount range; and a gain control unit for increasing a gain to an output signal of an image sensor as the photometry amount is smaller when the photometry amount is not within the light amount range and setting the gain to a constant value when the photometry amount is within the light amount range, an image capturing apparatus including the exposure control apparatus, and a method of controlling exposure using the apparatus.